Sen. John Thune, South Dakota Republican, said new reports of two downed fighter jets in Eastern Ukraine demonstrates some of the capabilities pro-Russia separatists have and how important it is that the United States stops any arms flow from Russia into Ukraine.

“More evidence, again, that these folks have bad designs and a capability to carry out these types of attacks,” Mr. Thune said on MSNBC’s “Morning Joe.”

Ukraine’s Defense Ministry said two Ukrainian fighter jets were downed Wednesday in areas of the country controlled by the separatists, AP reported.

“In all these things, all signs point back to Putin,” Mr. Thune said. “It’s very clear the pattern here. I think the narrative continues to build, and it should intensify the pressure on the Europeans to join the United States and others to try to put more pressure on the Russians. This has got to stop. And obviously, there’s a lot of harm that’s already been done and more that can be done if we don’t get it under control.”